Hu Chun Yi

Self-propagating high-temperature (combustion) synthesis (SHS) of powder-compacted materials

Self-propagating high-temperature synthesis (SHS) of powder compacts is a novel processing technique currently being developed as a route for the production of engineering ceramics and other advanced materials. The process, which is also referred to as combustion synthesis, provides energy- and cost-saving advantages over the more conventional processing routes for these materials. At the same time, the rapid heating and cooling rates provide a potential for the production of metastable materials with new and, perhaps, unique properties. This paper reviews the research that has been, and is being, undertaken in this exciting new processing route for high-technology materials and examines the underlying theoretical explanations which will, eventually, lead to improved control over processing parameters and product quality.

Combustion synthesis of TiNi intermetallic compounds

The synthesis of the TiNi intermetallic compound using the thermal explosion mode of the combustion synthesis technique has been used to determine the heat of fusion, ΔH m (7.77 kcal mol −1 ), of the TiNi intermetallic and the heat capacity, C p , (17.96 cal mol −1 K −1 ), of the liquid-phase TiNi. The effect of heating rate and degree of dilution of the Ti+Ni powder compact reactants with previously synthesized TiNi on the ignition, T ig , and combustion, T c , temperatures in an argon atmosphere have been determined

Preparation of calcium aluminate matrix composites by combustion synthesis

CaO–Al2O3–TiB2 composites have been produced by the Combustion Synthesis technique. These materials have matrices based on binary calcium-aluminate compounds, i.e., Ca3Al2O6 (C3A), Ca12Al14O33 (C12A7), CaAl2O4 (CA), CaAl4O7 (CA2) and CaAl12O19 (CA6). Except for samples with the matrix composition of C3A, the combustion synthesis reactions can be characterized as stable self-propagating waves with combustion temperatures ranging from 2125 K to 2717 K and combustion wave velocity from 4.0 mm/s to 10.6 mm/s. For samples with a matrix composition of C12A7, CA, and CA2, predominantly equilibrium compound phase was formed, while for samples with a matrix composition of C3A, non-equilibrium phases were also present. There was no evidence of CA6 formation for samples with a matrix composition corresponding to CA6.

The combustion synthesis of Ni-Ti shape memory alloys

Combustion synthesis is a new and promising method of producing Ni-Ti series shape memory alloys. It has the advantage of both time and energy savings compared with the conventional melting or powder metallurgy approaches. The value of the ratio ΔH∘ƒ,298/ Cp,298 plays a key role in this method, especially if a liquid product is required. Solidified products made by the combustion synthesis process were hot rolled into plates exhibiting the shape memory effect. It was discovered that shape memory transition temperatures can be tailored over a wide temperature range (from −78 to 460°C) by substituting a third element, such as palladium or iron, for nickel. This approach should greatly extend the application of such alloys.

Combustion Synthesis of Aluminoborate Glass Matrices

Combustion synthesis or self-propagating high-temperature synthesis (SHS) has been used for the first time to produce glass–ceramic materials. The materials produced by the technique have a glassy matrix (aluminoborate glass) and crystalline TiB2 particles, of about 0.5 μm. The combustion characteristics and microstructures of the synthesized materials are presented.